Analysis of Stochastic Nature and Shock Wave Pressure of Pulsed Spark Discharge in Saline With Auxiliary Pre-Electrolysis Pulse

Abstract

Intravascular lithotripsy through liquid-phase discharge is of great significance in improving the success rate of intravascular stent placement and treatment of severely vascular calcific plaque lesions. However, pre-breakdown delay in intravascular lithotripsy system discharge has strong stochastic nature for the same high voltage discharge pulse, thus causing wider range of shock wave pressure, shorter electrode life and higher treatment risk. To achieve controllable shock wave pressure, four discharge modes with different duration of auxiliary pre-electrolysis pulse were proposed and the influence of discharge stochasticity on the shock wave characteristics were investigated, along with mechanism analysis. The experimental results reveal that the discharge stochasticity can be greatly reduced in the optimal discharge mode with the auxiliary low-voltage pulse for saline pre-electrolysis applied before the main high-voltage discharge pulse. Unlike the original mode with merely applying main high-voltage discharge pulse, the pre-breakdown delay and shock wave fluctuation can be improved from 210–1070 ns and 2.79–3.97 MPa to 94–254 ns and 3.91–4.22 MPa, respectively. Moreover, the pre-breakdown stage of discharge is shortened and the energy deposition efficiency is significantly increased from 67.63% to 84.55%, which is probably caused by the promotion of the streamer formation with the pre-generated micro-bubbles from the pre-electrolysis pulse.